Yeah that would suck if you have a older Sonos streamer and then buy new one for another room, you update to latest app but then the older one does not work, it may either ignore the older player or refuse to run saying you have a legacy product. I have no problem running original squeeze devices squeezebox, a Logitech squeezebox, and a Logitech squeezebox touch, on a new fast quad core Synology Nas with pinkdot despite no longer getting official updates, it gets updates from pinkdot and runs on new Nas devices.
When I installed Sonos app on my phone I looked for after market players but there are none. Bad idea, if the app no longer works on your phone say if you have older phone but want latest app, it may not install.. or Sonos stop support you are screwed.
Also I REALLY didn't like you had to create an account online before the Sonos even allowed you to start using the product, since I don't have internet connection at home there is no way to set it up, I had to set it up round brothers first then take it home. Damn annoying. Also it does some kind of weird network setup or when I simply disconnected from brothers and connected to mine it should simply work, but I had to do a partial reset, not the email login wizard but telling it connect to existing system, go back and forth on setup on app and finally worked.
Also if Sonos stop support on older products what happens when you want to do the initial setup and you can't because it doesn't allow you to find old products?
Bit like having windows 7 machine on your home network, you buy a new second pc and the windows networking on windows10 doesn't connect to your windows 7 machine.
All this and the 65,000 track limit really makes me glad of squeezebox, and despise "apple-like" products.